Grid structure for electron tubes



Dec. 9, 1952 R, R LAW 2,621,303

GRID STRUCTURE FOR ELECTRON TUBES Filed July 50, 1948 2 SHEETS-SHEET 2Snventor RUSSELLRZAW g www d. 9M

Cttorneg Patented Dec. 9, 1952 UNITED STATES FA'KENT OFFICE GRIDSTRUCTURE FOR ELECTRON TUBES Application July 30, 1948, Serial No.41,576

11 Claims. (Cl. 313-348) In this application, I disclose improved gridelectrodes and an improved method of and apparatus for fabricating metalgrid electrodes. My method and apparatus is especially useful for makinggrid electrodes which comprise a support or supports, and a plurality ofmetal grid elements fastened thereto. The grid structures may be made ofvarious metals appropriate for such use. In preferred embodiments, Iused tungsten elements or Wires and copper supports. Because of theunusual properties of tungsten, such a grid possesses a number ofdesirable properties. For example, a tungsten-wire grid is strongmechanically, it is a good heat and electrical conductor, and iinally itis not damaged by overheating. The high thermal conductivity of thecopper supports contribute to and enhance these desirable qualities.

Heretofore, tungsten elements have been fastened to other metals by spotwelding. However Welds to copper can be accomplished only with greatdiiiculties. Moreover, it would be impractical to weld a large number offine Wires such as make up a grid electrode to the support member ormembers. Soldering in accordance With known practices would beimpossible especially when the supports are good heat conductors sincethe supports Would become so hot that all joints would run and While oneelement is being soldered to the support, other elements would becomeunsoldered.

An object of my invention is to provide a more practical method offastening metal elements such as used in grids to the support orsupports therefore and improved apparatus for carrying out said improvedmethod. In a sense, it might be said that an object of my invention isto provide a metal bonding process to replace spot welding Where use ofthe same is impractical. My invention, of course, goes much farthersince it involves a practical method of and means for assembling gridelectrodes and the like and fastening the grid elements to their supportor supports. This object is attained in accordance with my invention byassembling the grid wire elements on the support or supports in a novelmanner, restraining the grid elements as assembled in a novel manner,applying solder to all of the joints and heating the assembly until thesolder runs to form the bonds.

A further object of my invention is to provide improved grid structuresfor use in electron discharge devices, which grid structure may bereadily fabricated in accordance with my improved method.

A further object of my invention is to provide jigs for holding the gridsupports, and grid elements in place as desired during the novelfabricating process described briefly above.

In describing my invention in detail, reference will be made to theattached drawings in Which Figures l, 2 and 3 illustrate three gridelectrodes arranged in a novel manner to be fabricated in accordancewith my invention. Figures 4, 5 and 6 illustrate details of theembodiment of Figure 2 and of my novel jig apparatus for assembling anelectrode structure as illustrated in Figure 2 and holding the severalelements in exact position While the same are being soldered and forapplying the solder to all of the elements simultaneously. Figures 7, 8and 9 illustrate details of the embodiment of Figure 3 and details of mynovel jig for assembling the electrode structure and holding the severalelements in the exact position desired while the same are being bondedand the method of applying the solder to the elements.

My novel grid electrodes may as illustrated in Figures 1, 2 and 3comprise a cap member E, a base member 8 With a cylindrical portion I0and a conical portion I2 and a base flange I4, the conical portion I2and flange I4 being slotted and splayed to minimize diiculties fromdifferential thermal expansion between the grid base member and thesurface of the support to which it is fastened. In practice it was foundthat a base member that was not slotted and splayed as described hereinbecame distorted and Warped to such an extent that the grid structurecame apart and Was no longer useful. The elements IIS, as stated above,may be of metal of various types but are in the embodiments beingdescribed of tungsten and are disposed in parallel relation on or nearthe outer peripheries of the cap 6 and cylindrical portion I0 of thebase 8. In Figure 1, the elements I6 are retained in openings E and I0provided respectively in the cap member 6 and base member I0. In Figure2, the elements I6 are to be disposed in notches 6 and I0 in the outerperipheries of elements 6 and Ill. In Figure 3, the grid elements I6 areto be retained in notches on the outer periphery of cap member 5 andspaced along the inner periphery of the cylindrical portion I0 of thebase member.

It is essential that the elements I6 be electrically and thermallysubstantial integral with the supports 6 and 8. This is especiallynecessary Where the grid structure is to be used in U. H. F. amplifiersor oscillators. Moreover, it is essential that the elements I5 be strongmechanically and be good heat and electrical conductors, and that theelements 6 and 8 be good heat conductors and of the required strength.In the embodiment being described, the members I6 are tungsten rods,bars, or wires and the cap E and 5 base plate 8 are copper.

Since as stated above it is not feasible to spot weld the elements i6 tothe cap and base members, I propose to solder these joints. Solderhaving a high melting point that stands up well 10 under hightemperature and which maires a strong joint is to be used. In., anembodiment oai, my invention, eutectic silver solder (70% silver- 30%copper) was used. It was found that silver solder did not wet thetungsten members well and 15 to improve this part of the process,thetungsten Wires I6 were rst nickel plated. A grid structure asdisclosed in Figure 1 was built. The tungsten Wires i6, of sucientlength, were inserted inthe holes S and IQ', in the members ii and iii.The 2Q holes-Ill arein'eiect circular recesses in theend of cylinder my,havinga. depthyof -twice `thegdiamete1';of the wiregridelements.` The-wires isf were passed through theopeningsf inY theouter periphery; ofgrid cap,6A andftted intofappro- 25 priate holes le. Thefcap-memberfwas. spaced from the base member Sfthe: proper distanoeandl heldparailelthereto by ajiglin the formi-of -a base element such as at gegendpositioninggandspacing elements ysuolrasqat 22fand 2,4,fa1l of 3o Figuredeep7, withineans such-v asfarod28 te holdv the-jig l/elenrentsinVposition; The grid. base 8 Vmay' thenbeplaced onxthe-jigbase--26h-overlv the ;member 22' also' on -theyjigbase The spacer 2limaybeputfin place-,and theipin `inserted,` .as Ringso solder 2i werethenfpositioned around; the wires near,` the joints andtheassembledelements and jig were placedyinanoven*in an atmosphere ofhydrogen and-iired1 tomeltthesilver solder which runs rreelyalongthe:tungsten 4orods to form goodjoints'between thezrods and supports. The assembledgrid is then removed" from the furnace and if necessary the ends -of thetungsten -wires trimmed Orff-,close tothe` cap, member 6.`

In many cases it is-desirable-ito haveaoutward, curvature 1 of ythegridelements as Yshown irl-:Fige-l ure12in ordern-that fthe wiresfshallnotinad vertently boweinward.k Thisieature of thestruc ture isAimportant because Yif one of-thewiresis 5o bowed inward vrnoretlfianitsneighborsy it will;- receive more than its `proportionate share-of` gridcurrent ,andl will become hotter Iand bow inward. still further until iteventually-touches the cath-r ode tofthereby'cause failureof "thetubeVIn this-55- embodiment to. simpiify thegrid structure andfabricatingprocess, the outereperipherieseof the..r grid cap 5 and gridb-asecylinder mare slotted at 6 and lifrespectively -to receive the.grid.. elements I6 as shown in Figures 2a, 4, 5 and 6; so To obtain thisgrid form `and further facilitate assembly of the elements and bonding-oi'the same, I provided additional improvementggtormy, grid makingjigias illustrated in Figures 4,45 and` 6 to hold the gridelementsasdesired. This jig,65 comprises as described-amitiera base-plate 24),.lower body member 22; upperbodymember 2d` and jig cap member 25.- Thesemembers .arereeY tained in the desired position bythe-rod orshait Z8.The jig members-wand 22,1or2,22.and24 7o or 22 and 24 may'bea-singlepieoefandmay ,be made of any appropriate material. These meme.bers 2G, 22,' 24 and 26 .areinthe embodiment. being described of.stainless-steel,v each .thereofVA beingebored to accommodate thecenteringshaft v75 23. The base member 8 of the grid structure rests onthe jig base plate 29 and the circular lower body 22 of the jig has anouter periphery at the top which fits loosely into the portion I0 of thegrid structure` The outer periphery of the grid cap member B and of thegrid base member I0 are slotted at G and lll to receive the grid elements IS. After the members Ieare in zplace, a retaining ring 38 is putin place to hold the members I6 snugly Within the slots in the gridsupport iii. The upper body member 24 of the jigholds the grid cap 6parallel to the grid base 8 and at the desired distance therefrom. Thegridelements Vare fitted into the slots on the outer periphery :of thecap ii. The diameter of the cap 5 and the inner diameter of the axialflange ZTon the ylower end of the jig cap 26 are such that this axialflange 2'! bends the upper ends of the tungsten members I6 inward towardthe axis of the jig to bulge these members outwardly along-the portionbetweenwthe-.grid','capd6 and grid; base 8-for the purposedescribedaaboye;

In practice,l the jig= is assembled with the grid` base 8-onrthezjiggpbase 29% and the jg member` 22-: Within the gridybase; AringjofmseldereZl-isa placed ongthe upperfsurface of-,gridbase-memberldand the spacer Mois placed onfthe-jigmember: 22 with the: grid capl-on topK of fthe-spacer` 24; A second solder ring*v 2i is 'placed on-the:cap-:6LV adjacent the outer periphery f thereofY and-' thee jig vtopymemberi-2ii-isf placed -on thea-grid cape/(iil and centered byvjigcenteringpin` 28.- The.re taining rineizSU .is dropped -in piace.(before-mem-f ber 25 is assembledif desired). andrestseon-i shoulder 3eofY thegridr base ser. Then fthe tung-rl member. ZSsremoVed andtheexcess.v tungsten grid.

elements trimmed on" or otherwise removed.` Ther. jig; forms`aredisassembled1 and .themgrid iaready for use.`

nthe embodiment of Figures 3 7, 8.and.9,.thep grid elements IE areassembled with respec,t-to. and -bonded to the gridcap as illustrated,in Figuresge, dand 6.- The/portionei@ofthe-bases member in thisembodiment isi-not slotted to ref,-y ceive Athe elements c! 5 .f TheVouter top periphery f of :the stainless steelu'ig base member-,22 fis.slottedf asshown at r'22.iin'Fi'gures. 3 ;and;3c.: The fdepthf; of theslots andfdiameterfofthe base `member 22;? is `such that thegrid-elements :IGA-it .'.snuglybeiv tween grid .base member i0 .andfjigmemberllsi The grid andjig is assembledas described above and the wiresl-lare'slid up under faxial ilangel; and then retractedfas -they arebent ixivvardlyea-tfy the bottom-l ends and slid intorth'e 'slots -inthe@ periphery ofthe base'member-QZ; solder-ring 2l has been-placedinthe 'outer periphery olf-then grid cap E as described aboveand-a'secondsoldery ringl is placed on the upper end-of 'the'cylindr-i-e cal portionI of base member ;3: Note that'the` need of theretaining-ring of*the-embodiment of Figures `Li, 5 and 6 has beeneliminat-e'din'theembodiment of Figures. 3,"7," d andil." The ase' sembled 'apparatus isredjn an atmosphere:of j hydrogen, the jig member 26"removed,l3andfthe'excess portions of wires I6 trimmed as described above.

I have disclosed Various embodiments of my improved grid, and methodsof, and a jig for fabricating the same but this is by way of exampleonly and Various modifications may be made without departing from thespirit of my inventions.

I claim:

1. In a grid structure for an electron discharge device, a circular capmember wherein substantially equally spaced openings are provided in thebody thereof, an annular base member and a plurality of grid elementseach fastened at one end in a different one of said openings in said capmember, each element being fastened at its other end to a dierent pointon said base member, said last named points being substantially equallyspaced in said base member.

2. In a grid structure for an electron discharge device, an annular capmember wherein are formed substantially equally spaced openings near aperiphery of the cap member and in the body thereof, an annular basemember wherein are formed substantially equally spaced openings near aperiphery of the base member and in the body thereof and a plurality ofelongated grid elements each fastened at one end in a different openingin the cap member, each element being fastened at the other end in adifferent opening in the base member.

3. In a grid structure for an electron discharge device, an annular capmember wherein are formed substantially equally spaced recesses alongthe outer periphery thereof, an annular base member having a cylindricalportion wherein are formed substantially equally spaced recesses on theouter periphery thereof, and a plurality of elongated grid elementsfastened at one end in the recesses in said cap member and fastened atthe other end in the recesses in said base member and a retaining ringsurrounding said grid elements.

4. In a grid structure for an electron discharge device, an annular capmember wherein are formed substantially equally spaced recesses alongthe outer periphery thereof, an annular base member, and a plurality ofelongated grid elements fastened at one end in said recesses in theouter periphery of said cap member and fastened at the other end tosubstantially equally spaced points along the inner periphery of saidbase member.

5. A grid structure for an electron discharge device, comprising acircular cap member, an annular base member, and a plurality ofelongated grid elements fastened at their respective ends in the bodiesof said cap member and said base member, said elements being bowedoutwardly, from the axis of said members, intermediate the ends thereofand substantially parallel to each other and to said axis.

6. A grid structure comprising a base member and a plurality of gridwire elements secured thereto, said base member having a cylindricalportion to which the elements are fastened and a conical portionextending from said cylindrical portion to provide a mounting means forthe grid, said grid Wire elements being bowed outwardly from the axis ofsaid base member said conical portion being slotted and splayed toprevent the same from becoming deformed in the event of unduetemperature difference between the base element and structure to whichit is mounted.

7. In a grid structure as in claim l, each of said elements comprising asupporting core and a plating on the outside surface thereof, the corebeing of tungsten, and the plating being of nickel, said elements beingfastened to said cap and base members with silver solder.

8. In a grid structure as in claim 4, each of said elements comprising asupporting core and a plating on the outside surface thereof, the corebeing of tungsten, and the plating being of nickel, said elements beingfastened to said cap and base elements with silver solder.

9. The invention as described in claim 3 and wherein said grid elementsare bonded Within said openings to said cap member and base member.

10. A grid structure according to claim 3 wherein said retaining ringsurrounds the ends of said grid elements recessed in said base member.

11. In a grid structure for an electron discharge device, an annular capmember having substantially equally spaced openings in the body thereof,and annular base member, and a plurality of elongated grid elementsfastened at one end in said holes in said cap member and fastened at theother end to substantially equally spaced points along the innerperiphery of said base member.

RUSSELL R. LAW.

REFERENCES CITED rilhe following references are of record in the file ofthis patent:

UNITED STATES PA'I'ENTS Number Name Date 861,105 Genor July 23, 19072,005,257 Eitel June 18, 1935 2,228,939 Zottu et al. Jan. 14, 19412,264,735 Baker et al. Dec. 2, 1941 2,296,885 Vance Sept. 29, 19422,327,352 Hoover Aug. 24, 1943 2,359,769 Litton Oct. 10, 1944 2,380,525Hirmann July 3l, 1945 2,392,879 Radcliffe Jan. 15, 1946 2,402,119 BeggsJune 18, 1946 2,434,962 Rostas Jan. 27, 1948

